This invention relates to a pantograph apparatus capable of duplicating a variable number of copies from a single master pattern.
Pantographs which produce multiple copies from a master pattern are well known to those skilled in the art. These prior art pantographs have been proven to be generally unacceptable, however, suffering from a number of common disadvantages. One disadvantage generally shaped by the prior art as a whole is the presence of vibrational movement within the apparatus itself. This vibrational movement is usually caused by the motor driving the styluses. In efforts to solve this problem, various measures have been taken. The motor has been, in some instances, spaced apart from the work in an effort to isolate the vibration, with the styluses driven by an endless belt to form the copy. However, this approach necessitated the use of the parallelogram principal with its attendant problems of accuracy in reproduction.
Other problems are apparent in the prior art, most notably, that of accommodating objects of different diameters and widths, the most common approach being adjustment to a particular height through a shaft threaded for vertical positioning. Such an arrangement requires precise threading, gearing and strong support to accommodate the great weight necessary for the proper height adjustments. Other measures attempting to obviate the great expense associated with machining the precise threading and gears have included the use of counterweights which are adjustably displaced for vertical height adjustment. Still others have used a single helical spring in combination with the threaded shafts for height adjustment. However, it has been found that the use of a single spring on work pieces having variable thicknesses causes different biasing forces to be exerted by the stylus upon different portions of the copies, thereby occasioning inaccuracies in the copy at the extremities of the work piece, i.e., at the widest and narrowest cross sections of the work piece. Also, those work pieces uniformly very narrow in cross section would be subject to much less stylus pressure than those work pieces having a uniformly large cross section.